This invention relates to chaff-type countermeasures used by military aircraft and, more particularly, to a dispenser used to eject chaff-type countermeasures from aircraft.
Controllably deployable countermeasures of several types are used to deter and defeat attacks on aircraft by other aircraft, missiles, and antiaircraft artillery. Examples of such countermeasures include chaff employed to create false infrared or radar returns and flares that produce large heat signatures when viewed by infrared sensors. In each case, the countermeasure is deployed by an aircraft to confuse an attacker, and specifically the sensor used by the attacker, and to lure the attacker away from the deploying aircraft.
The present invention is concerned with dispensing chaff from the aircraft in a controlled manner. There are many types of chaff, including both passive chaff and active chaff. Examples include passive radar reflecting or absorbing materials, active combustibles or pyrophorics that generate heat in the infrared spectrum, and passive smoke or dust that obscures detection in the visible spectrum.
One type of chaff of particular interest is pyrophoric chaff. A pyrophoric material, such as described in U.S. Pat. No. 5,464,699, is coated onto thin strips of plastic that are encased in an air-tight film package. A large number of the individual packages of pyrophoric material are loaded into a dispenser and ejected when needed. As each package is ejected from the dispenser, the film is ruptured so that the pyrophoric material, upon contacting the air, ignites to produce an infrared signature. There may be several dispensers on the aircraft, each loaded with different types of pyrophoric materials. The types of pyrophoric material dispensed, the number of packages dispensed, and the rate and sequencing of the dispensing of the pyrophoric packages may be controlled to more-effectively simulate the heat signature of the engines of the protected aircraft than possible with conventional flares, thereby offering improved protection against infrared-sensor-guided attacks.
Pyrophoric-countermeasure dispensers are known, see for example U.S. Pat. No. 6,055,909, whose disclosure is incorporated by reference. Such dispensers must be controllable so that the packages of pyrophoric material may be controllably dispensed upon command. They must also provide maximum flexibility in use yet be standardized to minimize logistical support requirements. Dispensers such as that of the ""909 patent are fully operable and suitable for many missions, but the present inventors have recognized that, for other missions, they may have drawbacks.
There is accordingly a need for an improved chaff countermeasure dispenser. The improved chaff dispenser is needed for pyrophoric chaff, and for other types of chaff as well. The present invention fulfills this need, and further provides related advantages.
The present invention provides a dispenser structure for chaff countermeasures. The chaff dispenser is fully functional to deploy chaff countermeasures upon command, in the numbers and at the rates required by the countermeasure controller. The chaff dispenser structure is reusable, and may be reloaded either with the dispenser tube remaining on the aircraft or detached from the aircraft. The present approach is mechanically more robust that prior dispensers of chaff countermeasures. It also provides a basic chaff dispenser configuration that is readily used in a wide variety of sizes and capacities of chaff dispensers. The design is not complex, and there is a low parts count that reduces manufacturing costs and support requirements. Each chaff dispenser is suitable for modular assembly with other compatible chaff dispensers, to build up highly flexible countermeasure systems.
In accordance with the invention, a dispenser structure for chaff countermeasures includes at least one chaff dispenser. Each chaff dispenser comprises a dispenser tube having a tube sidewall, a dispensing opening, and a female thread structure in an inner surface of the tube sidewall. A male worm gear is threadably engaged to the female thread structure of the dispenser tube. A drive structure comprises a motor mount upon which the worm gear is rotatably supported. The motor mount is mechanically reacted, preferably against the dispenser tube itself, to prevent the motor mount from turning responsive to its own torque. A drive motor, preferably an electrical motor, is affixed to the motor mount and has a motor output connected to the worm gear to controllably turn the worm gear. At least one chaff countermeasure, and typically a plurality of chaff countermeasures, are disposed within the dispenser tube axially between the worm gear and the dispensing opening. A drive plate is preferably positioned between the worm gear and the at least one chaff countermeasure. There may be a pop-off cap overlying the dispensing opening of the dispenser tube that is pushed off when the motor operates to turn the worm gear and force the chaff material out of the dispensing opening.
The dispenser tube may have any cross-sectional shape. In one preferred embodiment, the dispenser tube has a prismatic cross-sectional shape such as a square cross-sectional-shape. In that case, the female thread structure is a segmented thread structure of noncontinuous threads in the prism faces.
The chaff dispenser structure desirably further includes a support housing in which the dispenser tube is received. The support housing allows at least two, and preferably a number of, the chaff dispensers to be connected together to form a dispenser array.
More generally, a dispenser structure for chaff countermeasures includes at least one chaff dispenser. Each chaff dispenser comprises a dispenser tube having a dispensing opening, and a drive structure comprising a motor that moves along the dispenser tube as the chaff countermeasures are dispensed from the dispensing opening.
The dispenser structure of the invention places a drive motor in each dispenser tube. The drive motor, operating through the worm gear, forces the chaff material, in packaged or unpackaged form, out of the dispensing opening of the dispenser tube upon command. The entire drive motor and worm gear move along the interior of the dispenser tube as the packages are dispensed. There is therefore no long drive shaft that must extend most of the length of the dispenser tube, so that the one type of drive structure may be readily used with any length of dispenser tube. Since the drive structure is the only part of the dispenser structure that requires significant maintenance, only a single set of spares or replacement parts is required.
The present design is also more robust than a dispenser design requiring a long shaft to push the chaff material out of the dispenser. A long shaft requires strong support bearings, and the shaft and bearings must be suitable to withstand large aircraft maneuvering forces when the shaft is fully extended. The dispenser tube must be made overly long to contain the full length of the shaft in its retracted position. The present approach, by contrast, moves the entire drive motor structure down the interior of the dispenser tube as the chaff is dispensed, so that the space within the dispenser tube is used most effectively and large shaft support bearings are not required. There is no long shaft cantilevered on bearings, so that the present design is more resistant to the forces generated during aircraft maneuvering. The same drive structure works equally well with dispenser tubes of any length and cross-sectional configuration.
With a modular support housing to support the chaff dispensers, arrays of such dispensers may be constructed in a bolt-together fashion, providing maximum flexibility for the countermeasures system.
The present dispenser structure and chaff dispenser are operable with a wide variety of types of chaff. The dispensing of pyrophoric chaff is of particular interest. However, other types of chaff such as aluminized plastic radar chaff, metallic chaff, and the like may be dispensed using the present approach.